The present invention relates to an apparatus having optical components which is designed for use in optical communication terminal equipment or the like, more particularly, the invention relates to improvement in an apparatus comprising an optical component such as an optical fiber mounted on a single crystal substrate such as a silicon substrate.
An apparatus having optical components is used in an optical communication terminal equipment for performing information communication between public telephones and between computers. The apparatus has a silicon substrate and optical components mounted on the substrate. The optical components include a semiconductor laser, an optical fiber and the like. The semiconductor laser which is a light source and an optical fiber are optically coupled with each other with high precision.
In general, the semiconductor laser and the optical fiber must be aligned with accuracy less than 1 .mu.m. For this reason, a silicon substrate has a V-shaped positioning groove (V groove) formed by high-precision anisotropic etching. Once set in the V groove, the optical fiber is positioned in a predetermined position.
In order to maintain the reliability of the apparatus, the semiconductor laser and optical fiber need to be sealed airtight and firmly fixed on the silicon substrate. To this end, a V-shaped fixing groove larger than the V-shaped positioning groove is provided at the middle part of the V-shaped positioning groove for receiving the bonding material. The optical fiber is fixed on the silicon substrate by means of solder material applied in the V-shaped fixing groove. And then, the fixed portion of the optical fiber and the semiconductor laser are covered with a cap or the like and sealed airtightly and watertightly.
However, an apparatus of this kind is disadvantageous in the following respects.
First, the bottom portion of the V-shaped fixing groove is so narrow that a gap is likely to exist between the bottom and the solder material exist in the V-shaped fixing groove. Thus, moisture may accumulate in the gap, possibly affecting the semiconductor laser.
Second the solder material in the V-shaped fixing groove may flow through a gap between the optical fiber and the V-shaped fixing groove into the V-shaped positioning groove. In the positioning groove, the solder material possibly contaminates an end face of the optical fiber.
Third, while forming the aforesaid V-shaped positioning groove by anisotropic etching, the etching mask may be displaced with respect to a crystal orientation of the single crystal substrate. Consequently, the V-shaped positioning groove may have a considerable size error. In other words, if the etching mask is so displaced, excessive etching happens because of the crystal orientation dependency of the etching rate due to atomic arrangement anisotropy, as will be described below.
Assume a sift angle .theta. is generated between the crystal orientation and the mask direction. An excessive etching width .DELTA.W and an excessive etching length .DELTA.L, these excessive etching widths .DELTA.W and length .DELTA.L are obtained from the following equations: EQU .DELTA.W=W(cos.theta.-1)+L sin.theta. EQU .DELTA.L=L(cos.theta.-1)+W sin.theta.
Where L is a desired length of the V-shaped positioning groove, and w is the desired width thereof.
If W=100 .mu.m and L=10 mm and .theta.=0.1.degree., the excessive etching width .DELTA.W will be 18 .mu.m. Hence, the size error will approximate to .+-.10%. Further, if the shift angle .theta. is 0.5.degree., the excessive etching width .DELTA.W will be 87 .mu.m. The size error will therefore be about .+-.45%, not allowable any longer.